The purpose of this research is to understand the role that gustatory cues play in the enhanced intake of lysine observed in lysine- deficient rats. It will be determined whether this enhanced intake is unconditioned or learned by measuring licking responses to brief taste trials of an array of amino acids. If this is an unlearned phenomenon a gustometer will be used to determine what peripheral gustatory nerves carry the lysine signal to the brain. If enhanced ingestion of lysine in response to deficiency is conditioned, licking will be analyzed to determine the time course and pattern leading to this adaptive ingestive behavior before peripheral nerve experiments are conducted. This research is important m that it relates basic sensory function (gustation) with an applied issue (nutritional deficiency). Because feeding is required for the survival and reproduction of all mammals, understanding the properties guiding it is relevant and may have implications related to eating disorders. Additionally, this project will provide insight into the neural and peripheral mechanisms used to detect amino acid imbalance, may add to our knowledge of learning processes as they occur under less constrained and biologically relevant contexts, and will reveal general principles that might be applicable to other nutritional substances, such as vitamins and minerals.